Bonaire’s Resilient Reefs Offer Hope for Dying Corals

BONAIRE, Dutch Antilles , Sep 29 2010 (IPS) - Scientists are closely examining the reefs of this island just north of Venezuela to determine why it has escaped the devastation that wiped out 85 percent of the Caribbean’s corals since the 1970s.

At this Bonaire reef, the olive-green coral is alive, but the mottled-gray coral is dead. Credit: Living Oceans Foundation/IPS

Just in the past 30 years, coral cover in the Caribbean has gone from a healthy 65 percent to perhaps 20 percent. New diseases and algae invasions have wiped out much of the corals that stretch from the southeastern U.S. state of Florida, where the coral cover is tiny, to Bonaire, where a good portion of those last 20 percent is located. The Caribbean coast of Central America is equally damaged.

Warmer, more acidic oceans predicted for the future because of climate change are expected to wreak even more devastation on the survivors. When the water gets too warm, the corals appear to beach and then usually die.

Though the Persian Gulf suffered a similar fate, mostly because of oil pollution, the Caribbean is by far the largest region to have lost most of its corals, which are colonies of tiny, individual animals that, like farmers, live off equally tiny algae.

“This means millions of people are losing an abundant supply of cheap, nutritious fish,” explains Andrew Bruckner, chief scientist of the Washington-based Khaled bin Sultan Living Oceans Foundation. In addition, he and other scientist say, corals are used for building materials, protection from waves and to attract tourists.

Bonaire, in contrast, enjoys exceptionally clear water, which has made it a diving Mecca since the 1970s. In a classic virtuous circle, the local government has successfully restricted fishing to keep the fish and coral reefs in good shape and the free-spending recreational divers coming.

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Still, diseases prevalent all over the Caribbean have almost wiped out the elkhorn and staghorn corals that once carpeted Bonaire’s shallowest parts, just off the beach, and provided habitat for myriad edible fish and crustaceans.

A little deeper, many of the massive star corals, key building blocks of reefs, have suffered the same fate, but quite a few are still alive.

On a recent morning in Bonaire, Bruckner, a coral scientist, laden with a scuba tank, a clipboard and measuring devices, wades into the water off one of Bonaire’s deserted, unspoiled beaches, known to divers as Taylor Made.

He is leading a team of a dozen colleagues on a week-long expedition to count dead and healthy corals, along with fish populations. Under water, Bruckner points to some of the last staghorns. Then we reach some giant star corals, up to six metres high, that are between 500 and 1,000 years old and he raises his thumb: they are olive green and healthy.

A little farther, other star corals are half olive green, half brown, separated by a whitish line. It’s called white plague disease, one of a family of pathologies that have decimated Caribbean corals. Bruckner gives a thumbs-down. But on many of the dead corals, he points to little lumps of live coral on the dead parts: thumbs-up again.

Back on the pebble beach, Bruckner takes off his mask and remarks, “What we’re seeing here is a reef that’s suffered from disease and bleaching, but the new corals tell us the reef is rebounding fast.”

That’s because there are still enough algae-eating fish around to keep the surface of the dead corals clean. It helps that there’s very little rain here and that hurricanes, which damage reefs, are rare. In the rest of the Caribbean, dead coral soon are covered with algae and the coral larvae have nowhere to settle, so after a hurricane, very little grows back.

But in Bonaire, Bruckner says far that far less degradation had occurred since 2005, when he last surveyed the island’s reef, than in the rest of the Caribbean in the same period.

Fishermen and polluters are only the most tangible killers of corals. But as the Earth gets warmer, hot-water spells wipe out entire reefs. The first major temperature spike came in 1998, and most Caribbean reefs never recovered. This year promises to be the hottest since 1998 in the Caribbean, and some coral die-offs have already been observed.

And if warmer water, a lack of algae-eaters and pollution were not enough, there’s another enemy lurking in the future: ocean acidification. As the carbon dioxide in the atmosphere has increased by a third in the past two centuries, a third of that increase has been absorbed by the oceans. The result is that ocean water is now more acidic than it was, which makes it harder for corals to build their skeletons.

The effects are already being felt. “In the Great Barrier Reef, the calcification rate has slowed 15 percent since 1990,” says Ove Hoegh-Gulberg, a coral biologist at the University of Queensland, Australia.

“Very few corals will survive this century and they will be in very bad shape,” adds Ken Caldeira of the Carnegie Institution.

But Bruckner is more optimistic. “The historical record shows corals are pretty adaptable,” he says over dinner at the divers’ hotel. “If we can restrict fishing and pollution and create more marine reserves, I think we can save some of the Caribbean’s coral reefs. But even if we don’t, in places like the remote Pacific islands, I think the more vulnerable coral species will die off and be replaced by tougher ones. I just don’t see them dying off completely.”

*This story is part of a series of features on biodiversity by IPS, CGIAR/Biodiversity International, IFEJ and UNEP/CBD, members of Communicators for Sustainable Development (http://www.complusalliance.org).